1. Field of the Invention
The present invention relates to a method of forming an O.sub.3 -TEOS oxide film, and more particularly to a method of forming an O.sub.3 -TEOS oxide film with improved substrate dependency.
2. Description of the Related Art
An O.sub.3 -TEOS oxide film formed by oxidation of TEOS (Tetraethylorthosilicate, Si(OC.sub.2 H.sub.5).sub.4) with O.sub.3 exhibits various superior film characteristics in planarization, step coverage, electrical insulation, etc. It has also received attention as an oxide film that can be formed by low-temperature growth at 400.degree. C. or less.
However, in forming an SiO.sub.2 film by oxidation of TEOS with O.sub.3, the film growth rate is extremely dependent on the property of a substrate layer formed on a substrate. That is to say, the so-called substrate dependency is remarkable. More specifically, the film growth rate of an SiO.sub.2 film to be formed by oxidation of TEOS with O.sub.3 on a hydrophobic substrate film such as an Si film, A1 film, or AP-CVD film (a substrate film incorporating a small quantity of H.sub.2 O) is different from that on a hydrophilic substrate film such as an SiO.sub.2 film formed by thermal oxidation (a substrate film incorporating a large quantity of H.sub.2 O). That is, the film thickness of the SiO.sub.2 film on the hydrophobic substrate film is small, whereas the film thickness of the SiO.sub.2 film on the hydrophilic substrate film is large. Further, the film growth rate depends also on the condition of end groups of components constituting the substrate film, thus rendering it unstable.
As described above, the SiO.sub.2 film formed by oxidation of TEOS with O.sub.3 is non-uniform in film quality and film thickness because of its substrate dependency, thus reducing the subsequent process margin and thus reducing product yield. To cope with this problem, it has been attempted to improve the substrate dependency of the SiO.sub.2 film produced using O.sub.3 -TEOS, by using HMDS (Hexamethyldisilazane, (Si(CH.sub.3).sub.3).sub.2 NH) and ethanol (C.sub.2 H.sub.5 OH) to carry out a treatment of the surface of a hydrophilic substrate film in a manner which renders it hydrophobic.
However, this conventional method requires additional apparatus for the hydrophobic conversion treatment of the substrate film, causing an increase in installation costs and in the number of process steps. Thus, there is a problem of increased operating costs inclusive of labor costs as well as costs involved with the transfer of the substrate between apparatuses.